Many vehicle control pedals can have or require non-linear responses. For example, vehicle clutch pedals typically require more force to initially disengage the clutch than they do further in their travel and vehicle engineers typically specify a desired force versus stroke curve that they wish the pedal to meet.
To reduce the force required to operate the clutch, or other control, during the beginning of the pedal stroke various assist mechanisms have been employed in the past. To date, one of the more common assist mechanisms has been a torsion spring connected between the pedal arm and the pedal mounting bracket. When the pedal is pressed to engage a control, such as a clutch, this spring biases the pedal towards the engaged position, reducing the amount of pedal force required to move the pedal through its initial stroke. As the pedal returns to its initial position, when the pedal is released, the spring is tensioned again, storing energy for the start of the next stroke. Other similar spring-based assist mechanisms are also known.
While the known spring assist mechanisms do work, they do suffer from problems. In particular, designing such a spring assist to meet a specified force versus stroke curve can be difficult or impossible. This difficulty is exacerbated by the fact that the assist mechanisms often act, at least to some extent, over the complete intended stroke of the pedal and thus desired assistance at one point of the stroke can have an undesired effect at other points in the stroke.